Variable-speed tail rotors for helicopters with variable-speed main rotors

Han, D. and Barakos, G.N. (2017) Variable-speed tail rotors for helicopters with variable-speed main rotors. Aeronautical Journal, 121(1238), pp. 433-448. (doi: 10.1017/aer.2017.4)

Abstract

Variable tail rotor speed is investigated as a method for reducing tail rotor power, and improving helicopter performance. A helicopter model able to predict the main rotor and tail rotor powers is presented, and the flight test data of the UH-60A helicopter is used for validation. The predictions of the main and tail rotor powers are generally in good agreement with flight tests, which justifies the use of the present method in analyzing main and tail rotors. Reducing the main rotor speed can result in lower main rotor power at certain flight conditions. However, it increases the main rotor torque and the corresponding required tail rotor thrust to trim, which then decreases the yaw control margin of the tail rotor. In hover, the tail rotor may not be able to provide enough thrust to counter the main rotor torque, if it is slowed to follow the main rotor speed. The main rotor speed corresponding to the minimum main rotor power increases, if the change of tail rotor power in hover is considered. As a helicopter translated to cruise, the induced power decreases, and the profile power increases, with the profile power dominating the tail rotor. Reducing the tail rotor speed in cruise reduces the profile power to give a 37% reduction in total tail rotor power and a 1.4% reduction to total helicopter power. In high speed flight, varying the tail rotor speed is ineffective for power reduction. The power reduction obtained by the variable tail rotor speed is reduced for increased helicopter weight.

• Item Type: Articles
• Additional Information: This work was supported from the National Natural Science Foundation of China (11472129), and Science and Technology on Rotorcraft Aeromechanics Laboratory Foundation (6142220050416220002).
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Barakos, Professor George
• Authors: Han, D., and Barakos, G.N.
• College/School: College of Science and Engineering > School of Engineering > Autonomous Systems and Connectivity
• Journal Name: Aeronautical Journal
• Publisher: Royal Aeronautical Society
• ISSN: 0001-9240
• ISSN (Online): 2059-6464
• Published Online: 23 February 2017
• Copyright Holders: Copyright © 2017 Royal Aeronautical Society
• First Published: First published in Aeronautical Journal 121(1238):433-448
• Publisher Policy: Reproduced in accordance with the copyright policy of the publisher